package org.esjsoftware.v2m.rim.util;

import java.io.IOException;

public class Base64 {
	private final static char ALPHABET[] = { 'A', 'B', 'C', 'D', 'E', 'F', 'G',
			'H', 'I', 'J', 'K', 'L', 'M', 'N', 'O', 'P', 'Q', 'R', 'S', 'T',
			'U', 'V', 'W', 'X', 'Y', 'Z', 'a', 'b', 'c', 'd', 'e', 'f', 'g',
			'h', 'i', 'j', 'k', 'l', 'm', 'n', 'o', 'p', 'q', 'r', 's', 't',
			'u', 'v', 'w', 'x', 'y', 'z', '0', '1', '2', '3', '4', '5', '6',
			'7', '8', '9', '+', '/' };
	private static int valueDecoding[] = new int[128];
	static {
		for (int i = 0; i < valueDecoding.length; i++) {
			valueDecoding[i] = -1;
		}

		for (int i = 0; i < ALPHABET.length; i++) {
			valueDecoding[ALPHABET[i]] = i;
		}
	}

	private Base64() {
	}

	public static String encode(byte[] data, int offset, int length) {
		int i;
		int encodedLen;
		char[] encoded;
		encodedLen = (length + 2) / 3 * 4;
		encoded = new char[encodedLen];
		for (i = 0, encodedLen = 0; encodedLen < encoded.length; i += 3, encodedLen += 4) {
			encodeQuantum(data, offset + i, length - i, encoded, encodedLen);
		}
		return new String(encoded);
	}

	public static String encode(byte[] data) {
		return encode(data, 0, data.length);
	}

	private static void encodeQuantum(byte in[], int inOffset, int len,
			char out[], int outOffset) {
		byte a = 0, b = 0, c = 0;
		a = in[inOffset];
		out[outOffset] = ALPHABET[(a >>> 2) & 0x3F];
		if (len > 2) {
			b = in[inOffset + 1];
			c = in[inOffset + 2];
			out[outOffset + 1] = ALPHABET[((a << 4) & 0x30) + ((b >>> 4) & 0xf)];
			out[outOffset + 2] = ALPHABET[((b << 2) & 0x3c) + ((c >>> 6) & 0x3)];
			out[outOffset + 3] = ALPHABET[c & 0x3F];
		} else if (len > 1) {
			b = in[inOffset + 1];
			out[outOffset + 1] = ALPHABET[((a << 4) & 0x30) + ((b >>> 4) & 0xf)];
			out[outOffset + 2] = ALPHABET[((b << 2) & 0x3c) + ((c >>> 6) & 0x3)];
			out[outOffset + 3] = '=';
		} else {
			out[outOffset + 1] = ALPHABET[((a << 4) & 0x30) + ((b >>> 4) & 0xf)];
			out[outOffset + 2] = '=';
			out[outOffset + 3] = '=';
		}
	}

	public static byte[] decode(String encoded) throws IOException {
		return decode(encoded, 0, encoded.length());
	}

	public static byte[] decode(String encoded, int offset, int length)
			throws IOException {
		int i;
		int decodedLen;
		byte[] decoded;
		if (length % 4 != 0) {
			throw new IOException("Base64 string length is not multiple of 4");
		}
		decodedLen = length / 4 * 3;
		if (encoded.charAt(offset + length - 1) == '=') {
			decodedLen--;
			if (encoded.charAt(offset + length - 2) == '=') {
				decodedLen--;
			}
		}
		decoded = new byte[decodedLen];
		for (i = 0, decodedLen = 0; i < length; i += 4, decodedLen += 3) {
			decodeQuantum(encoded.charAt(offset + i), encoded.charAt(offset + i
					+ 1), encoded.charAt(offset + i + 2), encoded.charAt(offset
					+ i + 3), decoded, decodedLen);
		}
		return decoded;
	}

	private static void decodeQuantum(char in1, char in2, char in3, char in4,
			byte[] out, int outOffset) throws IOException {
		int a = 0, b = 0, c = 0, d = 0, pad = 0;
		a = valueDecoding[in1 & 127];
		b = valueDecoding[in2 & 127];
		if (in4 == '=') {
			pad++;
			if (in3 == '=') {
				pad++;
			} else {
				c = valueDecoding[in3 & 127];
			}
		} else {
			c = valueDecoding[in3 & 127];
			d = valueDecoding[in4 & 127];
		}
		if (a < 0 || b < 0 || c < 0 || d < 0) {
			throw new IOException("Invalid character in Base64 string");
		}
		out[outOffset] = (byte) (((a << 2) & 0xfc) | ((b >>> 4) & 3));
		if (pad < 2) {
			out[outOffset + 1] = (byte) (((b << 4) & 0xf0) | ((c >>> 2) & 0xf));
			if (pad < 1) {
				out[outOffset + 2] = (byte) (((c << 6) & 0xc0) | (d & 0x3f));
			}
		}
	}
}